Surrogates can sometimes even bear a calf of a different species. The methodology of cross species embryo transfer has been used to produce calves of the Indian Gaur (left: this is an endangered species of wild cattle) with Holstein "mothers."
Because superovulation and embryo transfer works so very well in humans (in fact, humans are one of the most amenable species to such manipulation) superovulation and in vitro fertilization have become routine techniques in what is termed "assisted reproduction" for couples who may be naturally infertile.
Some very odd situations can be encountered. There are documented instances of women who serve as surrogate mothers for embryos not from strangers, but from their own daughters; in these instances, the "birth" mother is not the child's biological mother (technically) but she is the child's biological grandmother, sharing 25% of the child's genome!
Similar questions of dubious medical ethics and legalities don't arise in veterinary medicine, really, and embryo transfer following in vitro fertilization have been adapted as a means to make immense profit by cattle ranchers, dairymen, makers of liquid nitrogen, and other segments of the agricultural sector. It's becoming more common in small animal breeding as well.
There are many documented instances of surrogate mothers "renting" their uteri to hold a child for women who could not do it themselves; and in what is perhaps the most bizarre twist of this tale, one woman in the Republic of South Africa has provided a surrogate womb for her own daughter's child! Thus the biological mother and the birth mother are different, and the birth mother is really the child's biological grandmother.